1. Field of Invention
Exemplary aspects of the present invention relate to an image forming apparatus, a fixing unit, and an image forming method, and more particularly to an image forming apparatus, a fixing unit, and an image forming method with an enhanced cleaning mechanism for removing contaminants including toner particles.
2. Description of the Related Art
A background image forming apparatus, such as a copying machine, a printer, or a facsimile machine, forms an image on a recording medium (i.e., a recording sheet) in an electrophotographic or electrostatic method. Specifically, an electrostatic latent image is formed on a uniformly charged photoconductor according to image data. The electrostatic latent image is visualized with a developer (e.g., toner) to form a toner image on the photoconductor. The toner image is transferred onto a recording sheet and the recording sheet having the toner image is conveyed to a fixing unit in which heat and pressure fix the toner image on the recording sheet.
One example of a related art fixing unit includes a fixing roller including a heater and a pressure roller opposing the fixing roller. The fixing roller and the pressure roller respectively apply heat and pressure to the recording sheet to fix the toner image on the recording sheet while the recording sheet is conveyed through a nip formed under pressure between the fixing roller and the pressure roller.
Another example of a related art fixing unit includes a fixing belt, a heating roller including a heater, a fixing roller, and a pressure roller. The fixing belt is looped over the heating roller and the fixing roller. The pressure roller opposes the fixing roller via the fixing belt. The heating roller heats the fixing belt. The fixing belt and the pressure roller respectively apply heat and pressure to the recording sheet to fix the toner image on the recording sheet while the recording sheet is conveyed through a nip formed under pressure between the fixing belt and the pressure roller.
In the above-described fixing units, contaminants, including toner particles not completely fixed and paper dust, may be transferred from the recording sheet to the fixing roller or the fixing belt due to temperature and electrostatic factors while the recording sheet is conveyed through the nip formed under pressure between the fixing roller or the fixing belt and the pressure roller. The contaminants transferred onto the fixing roller or the fixing belt may be further transferred onto the pressure roller opposing the fixing roller or the fixing belt because the pressure roller is not configured to release the contaminants as easily as the fixing roller or the fixing belt. When the transferred contaminants are accumulated on the pressure roller, a part or all of the accumulated contaminants may be transferred onto a following recording sheet conveyed through the nip formed under pressure between the fixing roller or the fixing belt and the pressure roller. As a result, the recording sheet or the toner image on the recording sheet may be damaged.